I'm not sure if someone would know the answer but I'll ask anyway.I plan to increase the memory on my desktop, has an Asus P5Q Pro motherboard.Now I'm running on 6 GB (2x2GB + 2x1GB) G Skill DDR2 @ 1066, with timing 5-5-5-15.I could buy 4x4GB but I'll try to save some money first and try only 2x4GB and combining with the 2x2GB that I have now for a total of 12GB (which should be enough).

Problem is the new memory is not identical (I tried, I cannot find the one that I have as 4GB).So I can try only @800, with either 5-5-5-12 or 5-5-5-18. The current one should go down from 1066 to 800 without that many problems, but what timings do you think would have more chances to be compatible?Thanks

PS. or I should just buy 4x4GB as there will be too much headache combining?

"Always install DIMMs with the same CAS latency. For optimum compatibility, it is recommended that you obtain memory modules from the same vendor."

Here's probably one reason it seems slow -

"The system maps the total size of the lower-sized channel for the dual-channel configuration. Any excess memory from the higher-sized channel is then mapped for single-channel operation"

SO you only have 2 GB total in dual channel mode. The other 4 GB are in single channel mode. It would likely be faster (assuming memory is the bottleneck) if you either just removed the two 1 GB sticks or replaced them with another pair of 2GB sticks of same make.

You might be better off investing in a new MB with DDR3 and CPU if it is slow.

It's pretty fast usually, just occasionally in LR3 when I tried a little more cloning, etc slows down, and I see the memory use going up.Win7 64 prof, Intel Quad Q9550, OS on Intel SSD X-25M 160GB, storage on 2 WD Caviar 640GB (blue I think) in RAID0.

I plan to keep this computer for the next 2 years or so as I will be quite busy and probably I won't work that much on it. Plus it actually works pretty well overall. So the easiest would be to add some extra memory, everything else is pretty maxed out. I was thinking I could change a little the timings in the memory as the motherboard is pretty flexible about this things.

Maybe I got the instructions wrong, but I read the manual when I installed the memory sticks and followed their recommendations. I guess the easiest and most certain is to replace the 2 1GB sticks with 2GB sticks for a total of 8GB. Versus spending 300+ and try 16GB (as Newegg has pretty good return policy).

Try the memory upgrade scanner at http://www.crucial.com/. It'll tell you what memory you can use and how best to use it. It'll tell you what memory you have, what all possible upgrades are, and what would be best. Really useful software. I've used it on my Windows7 64 machine so know it'll work on Windows 7.Les

So far so good. I installed it and seems stable. I'll see later on if there is any significant change in performance.

In Windows Experience rating the memory went from 7.1 to 7.3.The weird part is that the processor also went up from 7.1 to 7.3, and also the 3D gaming went up a notch to 6.5. The desktop aero performance stayed the same at 5.9, while the hard disk performance went down to 7.5 from 7.6 (7.7 when I initially installed it).